Q: Tranny

The first thing that needs to be done is to scan the vehicle for all codes. Since the overdrive light is flashing, a simple code reader from your local parts store will not likely be of any help. Code readers are for engine related codes. They can’t access other systems like your transmission, ABS or body modules. Most of the time your check engine light will accompany a transmission code, so it is likely a transmission issue. This all means that you will need to take your truck into a repair shop that is good with electronic automotive systems, unless you have access to the needed equipment and the know-how yourself.

I have done some research on this issue and there seems to be about four scenarios that play out for this issue. Keep in mind, this is a complex problem that many technicians have been unable to diagnose and repair. With that said, there are a number of issues that create your situation.

1. Pinched wire in steering column at the selector lever: To confirm this, the steering column covers will need to be removed and the harnesses thoroughly inspected. This is the simplest repair of the four possibilities I found.

2. Powertrain control module (PCM) failure: If this is the case, have a veteran technician that you trust confirm this. It won’t likely be an easy diagnosis so be prepared for a significant amount of time spent to diagnose it.

3. Ignition coils: I found several cases where ignition coils were creating electrical noise throughout the electrical system causing this issue. Ignition coils are a common problem on the 5.4L motor. Again, this should be diagnosed by an experienced technician.

4. Wiring harness damage: There are a number of reports about wiring harness damage that can create symptoms such as this. Where they fail is not always easy to find. So this is another one that you will need an experienced technician to diagnose.

With some luck, you could have a simple shift solenoid failure. A good place to start is with a diagnosis of your check engine light by a qualified mobile technician who can come to your home or office. Consider YourMechanic.

I wish you luck.